Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA.
Department of Chemical and Environmental Engineering, University of California, Riverside, CA, USA.
Food Microbiol. 2019 Apr;78:134-142. doi: 10.1016/j.fm.2018.10.002. Epub 2018 Oct 9.
This study investigated the effects of solution chemistry and growth conditions on bacterial deposition on spinach leaf surfaces using a parallel plate flow cell. Two food safety pathogens of concern and two non-pathogen bacterial surrogates (environmental E. coli isolates) were grown in ideal (LB media) and nutrient-restricted (M9 media) conditions. Bacterial attachment was quantified as mass transfer rate coefficients for cells suspended in 10 mM KCl, CaCl and artificial groundwater, and cell and leaf surfaces were extensively characterized (zeta potential, hydrophobicity, extracellular polymer (EPS) composition). Between the pathogens, E. coli O157:H7 attachment was greater than that of Salmonella Typhimurium, attributed to measurable variability in cell surface charge and hydrophobicity. When grown in M9 media, both pathogens were significantly more adhesive to spinach surfaces (p < 0.01) than when grown in LB media. Surrogates did not follow this trend and showed minimal changes in adhesion kinetics and surface properties between growth conditions. EPS sugar/protein ratios were reduced in some of the highest attachment scenarios, suggesting that changes in EPS composition in favor of proteins may play a role. These results show the importance of growth conditions and solution complexities in understanding mechanisms of aqueous bacterial adhesion to food surfaces.
本研究使用平行板流池考察了溶液化学和生长条件对菠菜叶片表面细菌沉积的影响。选择了两种食源性病原体和两种非病原体细菌（环境 E. coli 分离株）作为研究对象，在理想（LB 培养基）和营养受限（M9 培养基）条件下进行培养。通过测量悬浮在 10 mM KCl、CaCl 和人工地下水的细胞的传质速率系数，对细菌的附着进行了定量分析，同时还对细胞和叶片表面进行了广泛的特征描述（zeta 电位、疏水性、细胞外聚合物（EPS）组成）。在两种病原体中，E. coli O157:H7 的附着量大于 Salmonella Typhimurium，这归因于细胞表面电荷和疏水性的可测量变化。当在 M9 培养基中生长时，与在 LB 培养基中生长相比，两种病原体对菠菜表面的附着能力明显更强（p<0.01）。替代物没有遵循这一趋势，在生长条件之间，其附着动力学和表面特性的变化很小。在某些附着情况较高的情况下，EPS 糖/蛋白比降低，表明有利于蛋白质的 EPS 组成变化可能起作用。这些结果表明，在理解水相细菌附着到食物表面的机制时，生长条件和溶液复杂性非常重要。
